The present invention relates generally to apparatus and methods for increasing the ability of pilots of high performance aircraft to resist high G caused unconsciousness, and more specifically to a novel improvement to anti-G suit valves that substantially increases their G-protective effectiveness.
While flying simulated or actual combat maneuvers, a fighter pilot's body undergoes very high accelerations from the rapid changes in speed and direction. These accelerations are generally expressed in units of G, equal to the acceleration of a mass at the surface of the Earth due to gravity. The accelerations of greatest concern to a pilot are those that occur along the vertical z-axis of the cockpit when the pilot pulls back hard on the aircraft control stick to accomplish a rapid climb or a fast banked turn. The pilot's oxygen-carrying blood is forced away from its regular path between the heart-lungs and the brain, and pools toward the blood vessels of his or her lower extremities. At sufficiently high G's, the pilot's field of vision narrows as blood flow to the retinas is reduced, called grayout, followed by blackout, and finally followed by loss of consciousness (called GLOC, for G induced Loss OF Consciousness) from insufficient blood flow to the brain.
Pilots fight the effects of high G's by straining maneuvers, tensing the muscles of their torso and extremities to squeeze shut the blood vessels and force blood flow to continue in the upper parts of their body. An anti-G suit helps this process by covering the pilot's legs and torso with air bladders which automatically inflate during high acceleration maneuvers to compress the blood vessels in those regions and force blood flow to continue to the brain. Because continuous compression of the blood vessels of the lower extremities is harmful, anti-G suits include an anti-G suit valve to restrict inflation only to periods of high acceleration.
The nearly instantaneous response of modern high performance jet aircraft causes acceleration onset rates (dG/dt or G') greater than the response time of typical anti-G suit valves, leaving the pilot both unprotected for periods of time sufficient to cause unconsciousness, and causing unconsciousness due to a high onset rate of acceleration at G levels lower than the pilot could otherwise tolerate.
To solve this problem, the prior art has introduced a variety of approaches to improve anti-G suit valve response times. Standard anti-G suit valves are mechanical spring-mass controlled valves, providing pressurized air to the anti-G suit bladders at pressures proportional to acceleration along the z-axis. A standard modification to such inertially controlled valves has been to make a so-called ready pressure valve which preloads the anti-G suit bladders to about 2 psi, a pressure easily tolerated by a pilot without significant discomfort, to reduce the delay in filling the bladders to an effective pressure once inflation is triggered.
Other prior art approaches attempt to fill the bladders to an effective pressure before the onset of adverse G effects. They include mounting an electrically activated solenoid over the mass to move the mass (and its attached valve spindle) when an accelerometer and accompanying circuitry detects preselected levels of acceleration (G) and rate of change of acceleration (G'). A variation of that approach fully opens the anti-G suit valve for a preselected period of time when the solenoid is first triggered, so that full protection is provided to the pilot as quickly as possible, then backs off to allow normal inertially controlled proportional operation.
Another prior art approach has been to add microprocessor controlled circuitry to control the solenoid mounted over the mass and valve spindle. The microprocessor controlled circuit can monitor the aircraft data bus to trigger inflation after receiving a signal, such as joystick movement, indicating that a high G maneuver is imminent. The prior art has also proposed adding software to such microprocessor controlled circuits to apply preselected pressure profiles that will maximize the ability of pilots to tolerate high G forces.
Many of the prior art improvements to anti-G suit valves are retrofits to existing anti-G valves. They are intended to be failsafe so that, in the event of failure of the improvement, the anti-G suit valve will default to its normal inertial operation.
These prior art modifications to anti-G suit valves are valuable improvements. Unfortunately, particularly in the case of microprocessor controlled anti-G suit valves, the prior art valve mechanisms do not provide precise control of the actual air pressure in the bladders, thus preventing realization of many of the desired benefits.
It is, therefore, a principal object of the present invention to provide a anti-G suit valve system that combines the rapid response of prior art anti-G valves with more precise control over the pressure inside the anti-G suit.
It is another object of the present invention to make it a retrofit to existing anti-G suit valves.
It is a feature of the present invention that its retrofit to existing anti-G suit valves will be inexpensive and straightforward.
It is another feature of the present invention that it is completely failsafe in operation so that, in the event of any failure, it will fall back to normal inertial valve operation.
It is yet another feature of the present invention that it can incorporate all the advantages of prior art anti-G suit valves while still fulfilling all its objects.
It is an advantage of the present invention that its feedback feature allows precise control of anti-G suit bladder pressures with relatively imprecise valves.